And with the first state primaries for the mid-term elections less than three weeks away, Director of National Intelligence Dan Coats told a congressional committee on Tuesday that the US was already "under attack".

WATCH: Director of National Intelligence Coats: “There should be no doubt that Russia perceives that its past efforts as successful and views the 2018 U.S. midterm elections as a potential target for Russian influence operations.” https://t.co/0ufYxak5lBpic.twitter.com/Gl9qR77nay

"There should be no doubt that Russia perceives its past efforts as successful and views the 2018 US midterm elections as a potential target for Russian influence operations," Mr Coats said.

The US elections in November, when Republican control of the House of Representatives and Senate are at stake, are shaping up to be extraordinarily competitive, raising fears that foreign influences could tip the balance in certain races.

How Russia could meddle in the process ranges from social media to misleading reports.

Social media

Shortly after the 2016 election, Mark Zuckerberg branded claims that Russia used Facebook to spread misinformation as "crazy". He has since backtracked on that as the scale of Russia's use of social media has emerged.

Facebook reported that 126 million Americans may have seen 80,000 Russian-backed political content on its platform over a two-year period. Twitter said 677,775 people were exposed to social media posts from more than 50,000 automated accounts with links to the Russian government.

Executives from both Facebook and Twitter have testified in Congress about Russia's purported disinformation drive aimed at US voters, with the election being seen as providing a fertile breeding ground for fake news.

Facebook’s tips for spotting fake news

Headlines such as "Pope backs Trump", "Hillary sold weapons to ISIS", "FBI Agent Suspected in Hillary Email Leaks Found Dead" went viral on Facebook in the run up to the election, garnering thousands of shares.

In November, Facebook handed over to Congress around 3,000 adverts bought by Russian operatives, with posts focusing on divisive issues such as immigration, gun control and gay rights.

But he admits Facebook, which boasts two billion daily users, cannot compete with misinformation campaigns designed by professionals who constantly "game the system".

Other propaganda

Beyond the spread of information and misinformation on social media, Russians have penned articles for opinion sites, such as CounterPunch, a left-leaning American news and opinion website.

In December, the Washington Post described one such freelancer called Alice Donovon, who wrote articles with a strong pro-Russian angle and who was tracked by the FBI. "Internal bureau reports described her as a pseudonymous foot soldier in an army of Kremlin-led trolls seeking to undermine America’s democratic institutions," the Post reported.

The five types of fake news

RT, the state-backed Russian news channel, has also been described by intelligence officials as the Kremlin’s “principal international propaganda outlet”.

It consistently featured negative stories about Mrs Clinton during the 2016 election campaign, according to United States intelligence officials.

And with 2.2 million YouTube subscribers, just slightly behind CNN, it managed to reach a huge audience.

Hacking of registration rolls and machines

Jeanette Manfra, a Department of Homeland Security official, said there was no evidence that any actual votes were manipulated.

The Department of Homeland Security later said hackers tested the systems in most states. In some they tried to infiltrate the system and failed, but in Illinois the systems were successfully breached.

People pull apart computers used in voting machines in a bid to uncover security bugs during a "hacker voting village" exercise at the Def Con hacking conference in Las VegasCredit: Reuters

“Unfortunately, there haven’t been widespread security improvements so far. We can be sure that our adversaries have been paying attention, and so they may be more likely to try attacking election systems in November,” J. Alex Halderman, the director of the Centre for Computer Security and Society at the University of Michigan, told the New Yorker.

Voters in different states will find different protections and systems. Only some will cast their vote with paper ballots - which obviously wards against hacking - or on machines that produce a paper backup.

"First we need to replace these older systems that don’t have a paper record, then we need to replace the other states' older equipment that’s vulnerable based on its age," Marian Schneider, president of Verified Voting, told Wired. "The question is whether they are going to be able to do it before 2018. You’d have to move pretty quickly to do it now."

The actions have raised fears hackers could infiltrate campaigns linked to candidates in the mid-terms and leak their e-mails to the public. With many of the races expected to be tight, such leaks could have the power to swing an election.

What has the Trump administration done?

Despite the warnings from top intelligence chiefs such as Mr Coats, not a lot has been done to counter the threats.

The Post has reported that US spy agencies planned "a half-dozen specific operations to counter the Russian threat", but, one year later, the Trump administration "remains divided over whether to act".

Part of the trouble stems from a lack of political will. Donald Trump has been loathe to accept his own intelligence agencies’ conclusions that Russia interfered in the US election and has described the former heads of the agencies as “political hacks”.

"He said he absolutely did not meddle in our election ... Every time he sees me, he says, ‘I didn't do that.’ And I believe, I really believe that when he tells me that, he means it," he said.

Congress could take action of its own. There are several bills, such as the Secure Elections Act, that seek to impose federal standards for voting machines, and provide funding to replace outdated equipment.

But even if the new legislation is passed before the elections, there would unlikely be enough time for the protections to be put in place by November.

"There has to be a sense of urgency and there doesn’t seem to be," Mr Schneider told Wired.

"People just need to put aside politics for one second and look at this in terms of a national security issue for our democracy. We really need to shore up election security, because this is the foundation on which everything rests."